Heat exchanger is a compact and efficient heat exchange equipment, and it is a good equipment for heating, cooling, heat recovery, rapid sterilization and other uses. However, due to the long-term operation of the heat exchanger, the different purity of cooling or heating side and the difference of process medium itself have made the heat exchanger scaling inevitable, which leads to the reduction of heat exchange efficiency of the heat exchanger, thus affecting the normal production and the safety of the equipment. Therefore, the heat exchanger should be cleaned regularly to remove dirt to ensure the high efficiency of heat exchange and normal production of the heat exchanger. Photo 1. The reasons, types and hazards of heat exchanger scaling 1. The three main reasons for fouling of heat exchanger (1) because most of the heat exchanger of heat exchanger is a heat exchange system with water as the heat carrier. Because some salts are precipitated from the water when the temperature and concentration are higher, they are attached to the surface of the heat exchanger to form scale. With the increase of service time and frequency, the scale layer gradually becomes thicker and harder, It is tightly attached to the surface of heat exchange pipe（ 2) As with scale, the other side of the heat exchanger fluid may have non scale solid precipitates due to the nature of the material itself, and it will accumulate more and more on the surface of the heat exchange pipe without treatment for a long time（ 3) When the organic matter of the fluid is more and the flow rate of the fluid is small, some mechanical impurities or organic matter will also deposit in the heat exchanger, forming loose, porous or colloidal dirt. 2. The six main fouling processes of heat exchanger are used for the common heat exchanger. According to the scaling mechanism, we generally divide the scale into the following categories: (1) crystallization and scaling: for example, water cooling system, because of the supersaturated calcium and magnesium salts in water crystallized from the water due to the change of temperature and pH, and then deposited on the surface of the heat exchanger, and thus formed the scale（ 2) Particle scaling: the accumulation of suspended homogeneous particles on the heat exchange surface（ 3) Chemical reaction scaling: the deposition of the same body caused by chemical reaction（ 4) Corrosion scaling: the heat exchange medium corrodes the heat exchange surface, and the corrosion products deposit on the heating surface to form dirt（ 5) Biological scaling: for the common cooling water system, industrial water towels often contain microorganisms and their required nutrients. These microbial groups reproduce, and their communities and their excrement form biological scale on the heat exchange surface with mud（ 6) Condensation and scaling: on the supercooled heat exchange surface, the high dissolved components of pure liquid or multi-component solution condense and deposit. The above classification only indicates that a process is a main process for the formation of such fouling. Scaling is often the result of the joint action of many processes. Therefore, the actual fouling on the heat exchange surface is often mixed with various kinds of dirt. 3. The harm of scale cleaning (1) scaling makes the heat exchange efficiency of equipment decrease greatly, energy consumption increases greatly, and production cost increases（ 2) Scaling makes the heat conduction condition of heat exchange equipment worse, and the heat transfer surface is overheated, which leads to blister, crack, tube explosion and other safety accidents（ 3) Scaling can cause corrosion damage under scale, cause equipment perforation and leakage, shorten the service life of equipment, scale will make the production process unstable, affect product quality and cause quality accidents.